Torsional active vibration control system

ABSTRACT

A damper mechanism for absorbing torsional vibrations in a rotating shaft. The damper mechanism includes a vibration absorbing mechanism and at least one actuator that is controllable to affect the torsional vibration absorbing characteristics of the vibration absorbing mechanism.

FIELD OF THE INVENTION

The present invention generally relates to devices for controllingnoise, vibration and harshness (NVH) and more particularly to a devicefor actively reducing or canceling vibration in a rotating shaft.

BACKGROUND OF THE INVENTION

Propshafts are commonly employed for transmitting power from arotational power source, such as the output shaft of a vehicletransmission, to a rotatably driven mechanism, such as a differentialassembly. As is well known in the art, the torsional loading of thepropshaft is rarely uniform over an extended period of time even atrelatively constant vehicle speeds and as such, the propshaft istypically subjected to a continually varying torsional load. Thesevariances in the torsional load carried by the propshaft tend to createtorsional vibrations which may generate noise in the vehicle drivetrainor vehicle that is undesirable to passengers riding in the vehicle. Inespecially severe instances, the vibration that is transmitted throughthe propshaft can generate fatigue in the propshaft and other drivetraincomponents to thereby shorten the life of the vehicle drivetrain. Thus,it is desirable and advantageous to attenuate vibrations within thepropshaft in order to reduce noise and guard against undue fatigue.

It is known in the art to provide tuned torsional vibrations dampers forattachment to shafts, such as crankshafts and propshafts, to attenuatetorsional vibrations. This approach, however, has several drawbacks. Onesuch drawback is that these devices are usually tuned to a specificfrequency and consequently, will only damp vibrations within arelatively narrow frequency band. Accordingly, these devices aretypically employed to effectively damp vibrations at a single criticalfrequency and offer little or no damping for vibrations which occur atother frequencies.

Another drawback with conventional mechanical damping devices relates totheir incorporation into an application, such as an automotive vehicle.Generally speaking, these devices tend to have a relatively large mass,rendering their incorporation into a vehicle difficult due to theirweight and overall size. Another concern is that it is frequently notpossible to mount these devices in the position at which they would bemost effective, as the size of the device will often not permit it to bepackaged into the vehicle at a particular location.

SUMMARY OF THE INVENTION

In one preferred form, the present invention provides a dynamic dampermechanism for damping torsional vibration in a shaft. The mechanismincludes a damper device having a mass member, an attachment member, avibration absorbing mechanism and at least one actuator. The attachmentmember is coupled for rotation with the shaft and the mass member isdisposed circumferentially about the attachment member. The vibrationabsorbing mechanism resiliently couples the mass member to theattachment member and has a torsional vibration absorbingcharacteristic. The actuator is coupled to the vibration absorbingmechanism and is operable in at least two conditions, with eachcondition affecting the torsional vibration absorbing characteristic ofthe vibration absorbing mechanism. The mechanism also includes a firstsensor, which is configured to sense a rotational position of the shaftand to generate a position signal in response thereto, as well as asecond sensor, which is configured to sense a magnitude of the torsionalvibration in the shaft and to generate a vibration signal in responsethereto. The controller receives the position signal and the vibrationsignal and controls the at least one actuator in response thereto tocause the at least one actuator to affect the torsional vibrationabsorbing characteristic of the vibration absorbing mechanism so as todamp the torsional vibration in the shaft.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims, takenin conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of an exemplary vehicle having a propshaftassembly constructed in accordance with the teachings of the presentinvention;

FIG. 2 is a perspective view of the propshaft assembly of FIG. 1;

FIG. 3 is an partially broken away front elevation view of the propshaftassembly of FIG. 1; and

FIG. 4 is a partially broken away front elevation view of a propshaftassembly constructed in accordance with the teachings of an alternateembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 of the drawings, a propshaft assemblyconstructed in accordance with the teachings of the present invention isgenerally indicated by reference numeral 10. The propshaft assembly 10is illustrated in operative associate with an exemplary vehicle 12. Thevehicle 12 conventionally includes a vehicle body 14, a chassis 16, asuspension system 18, a motor 20, a transmission 22 and an axle assembly24. As the construction and operation of the vehicle body 14, chassis16, suspension system 18, motor 20, transmission 22 and axle assembly 24are well known to those skilled in the art, these components need not bediscussed in significant detail.

Briefly, the suspension system 18 resiliently couples the axle assembly24 to the vehicle chassis 16. The transmission 22, which receives arotary output from the motor 20, includes a plurality of gear ratios(not specifically shown) that are employed to selectively change thespeed ratio of a transmission output shaft 22 a. Rotary power istransmitted via the propshaft assembly 10 to the input pinion 24 a of anaxle assembly 24. The axle assembly 24 operates to selectively directthe rotary power to a pair of drive wheels 26.

With additional reference to FIGS. 2 and 3, the propshaft assembly 10includes a propshaft 40 and a dynamic damper mechanism 42. The propshaft40 includes a tubular body 44 and a pair of conventional spiderassemblies 46. The spider assemblies 46 are coupled the opposite ends ofthe tubular body 44 and permit the propshaft 40 to be coupled to thetransmission output shaft 22 a and the input pinion 24 a in aconventional manner.

The dynamic damper mechanism 42 includes an inner ring 50, an outer ring52, a resilient coupling 54, an actuator 56 and a controller 58. Theinner ring 50 is coupled for rotation with the tubular body 44 of thepropshaft 40 by any conventional process, including fastening, welding,bonding and/or an interference fit (e.g. press fit or shrink fit). Theouter diameter of the inner ring 50 includes a plurality ofcircumferentially-spaced lugs 60 that extend outwardly toward the outerring 52.

The outer ring 52 is concentrically disposed around the inner ring 50and includes a sufficient amount of mass to accomplish the cancellationof vibration as will be discussed in detail, below. The inner side ofthe outer ring 52 includes a plurality of circumferentially-extendinglugs 62 that extend radially inwardly toward the inner ring 50. Each ofthe lugs 62 is disposed between a pair of the lugs 60. The lugs 60 and62 do not extend in so far in a radial direction that they contact theouter or inner ring 52 or 50, respectively.

The resilient coupling 54 maintains the concentric positioning of theouter ring 52 relative to the inner ring 50. The resilient coupling 54may include a plurality of compression springs or may be an elastomericmaterial as is shown in the example provided.

One or more actuators 56 are disposed between the inner and outer rings50 and 52 and in contact with the mutually opposed faces 60 a and 62 aof the lugs 60 and 62, respectively. The actuators 56 may use anyappropriate means to extend and retract between the faces 60 a and 62 a,but in the particular embodiment provided, the actuators includes amagnetostrictive member whose length may be changed by varying themagnitude of an electrical charge that is applied to it. The controller58 is electrically coupled to the actuators 56 and is operable forselectively controlling the charge that is applied to themagnetostrictive member.

During the operation of the propshaft assembly 10, the spring rate ofthe resilient coupling permits the outer ring 52 to damp vibrationswithin a predetermined frequency band. The controller 58, however, maybe employed to extend or retract the actuators 56 to change thetangentially applied load on the resilient coupling 54 to thereby affectthe spring rate of the resilient coupling 54. Those skilled in the artwill appreciate that the actuators 56 may be controlled so as tocancel-out torsional vibrations entering the axle assembly 24. Morepreferably, however, the actuators 56 are controlled so as to cancel outvibration that is generated by the axle assembly 24, including vibrationthat is generated by the meshing of the ring gear (not shown) and pinionaxle gears (not shown). As this vibration is typically a function of therotational speed of the propshaft 40, the response of the controller 58to a given propshaft rotational speed may be preprogrammed in a look-uptable 70. The controller 58 may utilize the existing vehicle sensors(not shown) and in-vehicle network (not shown) to determine therotational speed of the propshaft 40 and thereafter control theactuators 56 according to the parameters found in the look-up table 70.

Alternatively, the controller 58 may include one or more vibrationsensors 72 that are coupled to portions of the vehicle (e.g., the axleassembly 24). The vibration sensors 72 are operable for producing avibration signal in response to sensed vibrations. The controller 58responsively controls the actuators 56 so as to generate vibrations thatare of sufficient amplitude and shifted in phase to cancel out thevibrations that are sensed by the vibration sensors 72.

While the propshaft assembly 10 has been described thus far as includinga dynamic damper mechanism 42 that includes a resilient coupling thatconnects a pair of concentric rings, those skilled in the art willappreciate that the present invention, in its broader aspects, may beconstructed somewhat differently. As illustrated in FIG. 4 for example,the dynamic damper mechanism 42 may be constructed with a single ring100 having a plurality of pockets 102 and a plurality of actuators 104.The pockets 102, which are circumferentially spaced apart from oneanother, include a pair of opposite faces 106.

Each actuator 104 is disposed in a pocket 102 between the faces 106 andis selectively controllable to expand or contract in a direction that isapproximately tangential to the point at which it is mounted in the ring100. The actuators 104 may use any appropriate means to extend andretract between the faces 106, but in the particular embodimentprovided, the actuators 104 include a magnetostrictive member whoselength may be changed by varying the magnitude of an electrical chargethat is applied to the magnetostrictive member. The controller 58 iselectrically coupled to the actuators 104 and is operable forselectively controlling the charge that is applied to themagnetostrictive member.

The controller 58 controls the simultaneous actuation (i.e., expansionor retraction) of the actuators 104 to torsionally excite the ring 100.Like the dynamic damper mechanism 42, the actuators 104 of the dynamicdamper mechanism 42 may be controlled in a predetermined manner, such asbased on the rotational speed of the propshaft 40, for example, or inresponse to one or more vibration signals that are generated by anassociated vibration sensor.

While the invention has been described in the specification andillustrated in the drawings with reference to a preferred embodiment, itwill be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention as defined in the claims. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment illustrated by the drawingsand described in the specification as the best mode presentlycontemplated for carrying out this invention, but that the inventionwill include any embodiments falling within the foregoing descriptionand the appended claims.

1. A dynamic damper mechanism for damping torsional vibration in ashaft, the dynamic damper mechanism comprising: a damper device having amass member, an attachment member, a vibration absorbing mechanism andat least one actuator, the attachment member being adapted to be coupledfor rotation with the shaft, the mass member being disposedcircumferentially about the attachment member, the vibration absorbingmechanism resiliently coupling the mass member to the attachment memberand having a torsional vibration absorbing characteristic, the actuatorbeing coupled to the vibration absorbing mechanism and being operable inat least two conditions, each condition affecting the torsionalvibration absorbing characteristic of the vibration absorbing mechanism;a first sensor that is adapted to sense a rotational position of theshaft and generate a position signal in response thereto; a secondsensor that is adapted to sense a magnitude of the torsional vibrationin the shaft and generate a vibration signal in response thereto; and acontroller coupled to the first and second sensors and the at least oneactuator, the controller receiving the position signal and the vibrationsignal and controlling the at least one actuator in response thereto tocause the at least one actuator to affect the torsional vibrationabsorbing characteristic of the vibration absorbing mechanism so as todamp the torsional vibration in the shaft.
 2. The dynamic dampermechanism of claim 1, wherein the actuator includes a magnostrictivemember having a dimension that varies in accordance with a controlsignal that is produced by the controller.
 3. The dynamic dampermechanism of claim 2, wherein the vibration damping mechanism includes aresilient member that extends radially outwardly between the attachmentmember and the mass member in a compressed state, the magnostrictivemember being operable for varying a degree to which the resilient memberis compressed.
 4. The dynamic damper mechanism of claim 3, furthercomprising a plurality of second resilient members, each of the secondresilient members extending radially outwardly between the attachmentmember and the mass member in a compressed state and circumferentiallyspaced apart from one another and the resilient member.
 5. The dynamicdamper mechanism of claim 4, wherein a second magnostrictive member iscoupled to each of the second resilient members, each of the secondmagnostrictive members being operable for varying a degree to which anassociated one of the second resilient members is compressed.
 6. Thedynamic damper mechanism of claim 5, wherein the controller is operablefor controlling the magnostrictive member and each of the secondmagnostrictive members on an individual basis.
 7. The dynamic dampermechanism of claim 4, wherein the second resilient members are formedfrom an elastomeric material.
 8. The dynamic damper mechanism of claim3, wherein the resilient member is formed from an elastomeric material.9. The dynamic damper mechanism of claim 2, wherein the vibrationdamping mechanism includes a first resilient member and a secondresilient member, each of the first and second resilient members beingconfigured to exert a force in a tangential direction, the first andsecond resilient members being spaced apart from one another with one ofthe magnostrictive member, the attachment member and the mass memberbeing disposed therebetween.
 10. The dynamic damper mechanism of claim9, wherein at least one of the first and second resilient members is aspring.
 11. The dynamic damper mechanism of claim 10, wherein the springis a coil spring.
 12. The dynamic damper mechanism of claim 9, whereinat least one of the first and second resilient members is formed from anelastomeric material.
 13. A shaft assembly for transmitting rotarypower, the shaft assembly comprising: a shaft structure; a damper devicehaving a mass member, an attachment member, a vibration absorbingmechanism and at least one actuator, the attachment member being adaptedto be coupled for rotation with the shaft structure, the mass memberbeing disposed circumferentially about the attachment member, thevibration absorbing mechanism resiliently coupling the mass member tothe attachment member and having a torsional vibration absorbingcharacteristic, the actuator being coupled to the vibration absorbingmechanism and being operable in at least two conditions, each conditionaffecting the torsional vibration absorbing characteristic of thevibration absorbing mechanism; a first sensor for sensing a rotationalposition of the shaft and generating a position signal in responsethereto; a second sensor for sensing a magnitude of torsional vibrationin the shaft and generating a vibration signal in response thereto; anda controller coupled to the first and second sensors and the at leastone actuator, the controller receiving the position signal and thevibration signal and controlling the at least one actuator in responsethereto to cause the at least one actuator to affect the torsionalvibration absorbing characteristic of the vibration absorbing mechanismso as to damp the torsional vibration in the shaft structure.
 14. Theshaft assembly of claim 13, wherein the actuator includes amagnostrictive member having a dimension that varies in accordance witha control signal that is produced by the controller.
 15. The shaftassembly of claim 14, wherein the vibration damping mechanism includes aresilient member that extends radially outwardly between the attachmentmember and the mass member in a compressed state, the magnostrictivemember being operable for varying a degree to which the resilient memberis compressed.
 16. The shaft assembly of claim 13, wherein the vibrationdamping mechanism includes a first resilient member and a secondresilient member, each of the first and second resilient members beingconfigured to exert a force in a tangential direction, the first andsecond resilient members being spaced apart from one another with one ofthe magnostrictive member, the attachment member and the mass memberbeing disposed therebetween.
 17. A shaft assembly for transmittingrotary power, the shaft assembly comprising: a shaft structure; a damperdevice having a mass member, an attachment member a vibration absorbingmechanism and at least one actuator, the mass member being disposedcircumferentially about the shaft structure, the vibration absorbingmechanism resiliently coupling the mass member to the shaft structureand having a torsional vibration absorbing characteristic, the actuatorbeing coupled to the vibration absorbing mechanism and being operable inat least two conditions, each condition affecting the torsionalvibration absorbing characteristic of the vibration absorbing mechanism;a first sensor for sensing a rotational position of the shaft andgenerating a position signal in response thereto; a second sensor forsensing a magnitude of the torsional vibration in the shaft andgenerating a vibration signal in response thereto; and a controllercoupled to the first and second sensors and the at least one actuator,the controller receiving the position signal and the vibration signaland controlling the at least one actuator in response thereto to causethe at least one actuator to affect the torsional vibration absorbingcharacteristic of the vibration absorbing mechanism so as to damp thetorsional vibration in the shaft structure.
 18. The shaft assembly ofclaim 17, wherein the actuator includes a magnostrictive member having adimension that varies in accordance with a control signal that isproduced by the controller.
 19. The shaft assembly of claim 18, whereinthe vibration damping mechanism includes a resilient member that extendsradially outwardly between the attachment member and the mass member ina compressed state, the magnostrictive member being operable for varyinga degree to which the resilient member is compressed.
 20. The shaftassembly of claim 18, wherein the vibration damping mechanism includes afirst resilient member and a second resilient member, each of the firstand second resilient members being configured to exert a force in atangential direction, the first and second resilient members beingspaced apart from one another and being disposed on opposite sides ofone of the magnostrictive member, the mass member and a radiallyextending member that is fixedly coupled for rotation with the shaftstructure.